Filter media, elements, and methods

ABSTRACT

Fibrous filter medium that includes a surface-loading filter layer comprising fine fibers having an average diameter of less than 1 micron; a depth loading filter layer; and a support layer; wherein the layers are configured and arranged for placement in a gas stream with the surface loading filter layer being the most upstream layer.

CONTINUING APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.16/301,163, filed Nov. 13, 2018, which is the § 371 U.S. National Stageof International Application No. PCT/US2017/031222, filed May 5, 2017,which claims the benefit of U.S. Provisional Application No. 62/336,433,filed May 13, 2016, and U.S. Provisional Application No. 62/351,401,filed Jun. 17, 2016, the disclosures of which are incorporated byreference herein in their entireties.

BACKGROUND

Fluid streams, particularly air and gas streams, often carry particulatematerial therein. The removal of some or all of the particulate materialfrom the fluid stream is needed. For example, air intake streams to thecabins of motorized vehicles, air in computer disk drives, HVAC air,clean room ventilation air, air to engines for vehicles or powergeneration equipment, gas streams directed to gas turbines, and airstreams to various combustion furnaces, often include particulatematerial therein. In the case of cabin air filters it is desirable toremove the particulate matter for comfort of the passengers and/or foraesthetics. With respect to air and gas intake streams to engines, gasturbines and combustion furnaces, it is desirable to remove theparticulate material because particulate can cause substantial damage tothe internal workings of the various mechanisms involved. In otherinstances, production gases or off-gases from industrial processes orengines may contain particulate material therein. Before such gases aredischarged to the atmosphere, it is typically desirable to obtain asubstantial removal of particulate material from those streams.

Higher and higher efficiency filters are needed to get cleaner air orother gas streams. Low pressure is desired to have less restriction togas (e.g., air) flow caused by high efficiency filters. Also, longerlife is desired to reduce the maintenance and filter costs, which isoften a challenge in high efficiency filters. Thus, there continues tobe a need for high performance filters, i.e., high efficiency, lowpressure-drop, long-life filters.

SUMMARY

The present disclosure provides filter media and filter elements,particularly for gas (e.g., air) filtration applications.

In one embodiment, there is provided a gas filter medium (e.g., airfilter medium) that includes: a surface loading filter layer includingfine fibers having an average diameter of less than 1 micron; a depthloading layer; and a support layer. During use, the layers areconfigured and arranged for placement in a gas stream with the surfaceloading filter layer being the most upstream layer. That is, the layersare positioned relative to each other such that the surface loadingfilter layer is positioned as the first layer encountered by the gas(e.g., air) stream being filtered (i.e., the fine fiber filter layer isthe most upstream layer). In certain embodiments, filter media of thepresent disclosure are pulse cleanable.

In another embodiment of the present disclosure, there is provided a gasfilter element (e.g., air filter element) that includes a housing and afilter medium as described herein.

In another embodiment of the present disclosure, there is provided amethod of filtering gas (e.g., air), the method including directing thegas through a filter medium or filter element as described herein.

In certain embodiments, the depth loading filter layer includes ahigh-efficiency glass-containing filter layer, a melt-blown filterlayer, or a combination thereof. A high-efficiency glass-containingfilter layer may include glass fibers and multi-component binder fibers.A high-efficiency melt-blown filter layer may include fibers having anaverage diameter of 0.5 micron to 10 microns.

Herein, “high-efficiency” for a filter layer of the present disclosureis able to remove at least 55% (by number) of 0.4-micron size DEHSparticles at 4 feet per minute (ft/min or fpm) (i.e., 2 centimeters persecond (cm/sec)). For example, a filtration efficiency of at least 70%at 0.4 micron is considered “high efficiency.” In certain embodimentsherein, high-efficiency means removing at least 70%, at least 80%, atleast 85%, at least 95%, at least 99.5%, at least 99.95%, or at least99.995%, of such particles, at 4 ft/min (2 cm/sec).

Herein, “high-efficiency” for a composite filter medium (which may ormay not be corrugated) and/or filter element (which is typicallycorrugated and pleated) of the present disclosure displays an efficiencyof at least F9 per EN779:2012. Additionally, a “high-efficiency”filterelement (which is typically corrugated and pleated) of the presentdisclosure displays an efficiency of at least E10, or at least E11, orat least E12 per EN1822:2009.

The term “melt-blown fibers” refers to fibers formed by extruding amolten thermoplastic material through a plurality of fine, usuallycircular, die capillaries as molten threads or filaments into converginghigh velocity gas (e.g., air) streams which attenuate the filaments ofmolten thermoplastic material to reduce their diameter, which may be tomicrofiber diameter. Thereafter, the melt-blown fibers are carried bythe high velocity gas stream and are deposited on a collecting surfaceto form a web of randomly dispersed melt-blown fibers. Typically,melt-blown fibers are microfibers which may be continuous ordiscontinuous, are generally equal to or smaller than 20 microns (andoften 10 microns) in diameter, and are generally self bonding whendeposited onto a collecting surface. Melt-blown fibers used in thepresent invention are preferably substantially continuous in length.

The term “multi-component fibers” refers to fibers formed from at leasttwo polymers extruded separately but spun together to form one fiber. Asa particular example of a multi-component fiber, a “bicomponent fiber”includes two polymers arranged in substantially constantly positioneddistinct zones across the cross-section of the bicomponent fiber andextend continuously along the length of the bicomponent fiber. Theconfiguration of such a bicomponent fiber may be, for example, asheath/core configuration wherein one polymer is surrounded by anotheror may be a side-by-side configuration or an “islands-in-the-sea”configuration. For two component fibers, the polymers may be present inratios of 75/25, 50/50, 25/75 or any other desired ratios. Conventionaladditives, such as pigments and surfactants, may be incorporated intoone or both polymer streams, or applied to the filament surfaces.

The term “polymer” includes, but is not limited to, homopolymers,copolymers, such as for example, block, graft, random and alternatingcopolymers, terpolymers, etc., and blends and modifications thereof.Furthermore, unless otherwise specifically limited, the term “polymer”shall include all possible geometrical configurations of the material.These configurations include, but are not limited to, isotactic,syndiotactic, and atactic symmetries. The term “copolymer” refers to apolymer that includes two or more different monomeric units, therebyincluding terpolymers, tetrapolymers, etc.

The terms “comprises” and “includes” and variations thereof do not havea limiting meaning where these terms appear in the description andclaims. Such terms will be understood to imply the inclusion of a statedstep or element or group of steps or elements but not the exclusion ofany other step or element or group of steps or elements. By “consistingof” is meant including, and limited to, whatever follows the phrase“consisting of.” Thus, the phrase “consisting of” indicates that thelisted elements are required or mandatory, and that no other elementsmay be present. By “consisting essentially of” is meant including anyelements listed after the phrase, and limited to other elements that donot interfere with or contribute to the activity or action specified inthe disclosure for the listed elements. Thus, the phrase “consistingessentially of” indicates that the listed elements are required ormandatory, but that other elements are optional and may or may not bepresent depending upon whether or not they materially affect theactivity or action of the listed elements.

The words “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

In this application, terms such as “a,” “an,” and “the” are not intendedto refer to only a singular entity, but include the general class ofwhich a specific example may be used for illustration. The terms “a,”“an,” and “the” are used interchangeably with the term “at least one.”

The phrases “at least one of” and “comprises at least one of” followedby a list refers to any one of the items in the list and any combinationof two or more items in the list.

As used herein, the term “or” is generally employed in its usual senseincluding “and/or” unless the content clearly dictates otherwise. Theterm “and/or” means one or all of the listed elements or a combinationof any two or more of the listed elements.

Also herein, all numbers are assumed to be modified by the term “about”and preferably by the term “exactly.” As used herein in connection witha measured quantity, the term “about” refers to that variation in themeasured quantity as would be expected by the skilled artisan making themeasurement and exercising a level of care commensurate with theobjective of the measurement and the precision of the measuringequipment used.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range as well as the endpoints (e.g., 1to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Herein, “up to” anumber (e.g., up to 50) includes the number (e.g., 50).

The term “in the range” or “within a range” (and similar statements)includes the endpoints of the stated range.

Reference throughout this specification to “one embodiment,” “anembodiment,” “certain embodiments,” or “some embodiments,” etc., meansthat a particular feature, configuration, composition, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the invention. Thus, the appearances of such phrases invarious places throughout this specification are not necessarilyreferring to the same embodiment of the invention. Furthermore, theparticular features, configurations, compositions, or characteristicsmay be combined in any suitable manner in one or more embodiments.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

DRAWINGS

The disclosure may be more completely understood in connection with thefollowing drawings.

FIG. 1 is a cross sectional view of a portion of an embodiment of acomposite filter media of the present disclosure.

FIG. 2 is a cross sectional view of an embodiment of a composite filtermedia of the present disclosure.

FIG. 3 is a cross sectional view of an embodiment of a composite filtermedia of the present disclosure.

FIG. 4 is a perspective view of one embodiment of a filter elementusable in an air intake system.

FIG. 5 is a perspective view of another embodiment of another elementwith a filter medium of the disclosure.

FIG. 6 is a top plan view of another filter element of the disclosureusable in an air intake.

FIG. 7 is a front elevational view of the element of FIG. 6 .

FIG. 8 is a right side elevational view of the filter element of FIG. 7.

FIGS. 9-13 are schematic, cross-sectional views of further embodimentsof filter elements.

FIG. 14 is a perspective view of another embodiment of a filter element.

FIG. 15 is a perspective view of another embodiment of a filter elementhaving an ovate structure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure provides filter media and filter elements,particularly for gas (e.g., air) filtration applications.

In one embodiment, a gas filter medium (e.g., air filter medium) thatincludes: a surface loading filter layer comprising fine fibers havingan average diameter of less than 1 micron; a depth loading filter layer;and a support layer.

During use, the layers are configured and arranged for placement in agas stream with the surface loading filter layer being the most upstreamlayer. That is, the layers are positioned relative to each other suchthat the surface loading filter layer (i.e., fine fiber filter layer) ispositioned as the first layer encountered by the gas (e.g., air) streambeing filtered (i.e., the fine fiber filter layer is the most upstreamlayer).

In certain embodiments, filter media of the present disclosure are pulsecleanable. Pulse cleanable is important for self cleaning (e.g., viaback air pulses) and is useful when the filter medium is used for veryhigh dust concentration. Pulse cleanability can be determined accordingto the Modified ISO 11057 Test Method described in the Examples Section.

In certain embodiments, a composite filter media includes two or morefine fiber filter layers. In certain embodiments, a composite filtermedia includes two or more depth loading layers (e.g., glass-containingfilter layers, melt-blown filter layers, or combinations thereof). Incertain embodiments, a composite filter media includes two or moresupport layers. These layers can be arranged in a variety of orders aslong as one of the fine fiber filter layer is the most upstream layer.

Each filter layer and support layer can be a composite of multiplelayers. For example, a depth loading layer can be a composite of two ormore different layers of melt-blown fibers, either differing incomposition and/or fiber diameter.

In certain embodiments, a filter medium of the present disclosure has athickness of at least 10 mils (0.25 mm). In certain embodiments, afilter medium of the present disclosure has a thickness of up to 60 mils(1.5 mm), or up to 30 mils (0.76 mm).

As shown in FIG. 1 , which shows a portion of an exemplary compositefilter medium 10 of the present disclosure, there are at least twofilter layers, i.e., layers that perform filtration: a surface loadinglayer 20, and a depth loading filter layer (e.g., glass-containingfilter layer) 22. In one embodiment, as shown in FIG. 2 , which shows anexemplary composite filter medium 10 of the present disclosure, thereare: a surface loading layer 20, a depth loading filter layer (e.g.,glass-containing filter layer) 22, and a support layer 18 positionedbetween the depth loading layer 22 and the surface loading layer 20. Inanother embodiment, as shown in FIG. 3 , which shows an exemplarycomposite filter medium 10 of the present disclosure, there are: asupport layer 18; a surface loading layer 20, and a depth loading filterlayer (e.g., glass-containing filter layer) 22 positioned between thesupport layer 18 and the surface loading layer 20.

As shown in these exemplary embodiments, the surface loading filterlayer 20 is positioned upstream of the depth loading filter layer 22relative to the direction of gas flow (e.g., air flow) indicated by anarrow. That is, the surface loading filter layer 20 is the first layerencountered by the gas (e.g., air) stream during use.

The thicknesses of each of the filter and support layers may be the sameor different, and are not limiting. However, it is noted that thicknesshas an effect on filtration properties. The overall thickness of themedia is desirably minimized without significantly affecting the othermedia properties, such as dust loading capacity, efficiency, andpermeability. This allows for more pleats in an element, for example,preferably such that a filter element includes a maximum amount of mediawithout adversely affecting the filter element properties andperformance (e.g., efficiency, pressure drop, or dust loading capacity).

Typically, in a filter medium of the present disclosure, the filterlayers, and preferably, the filter and support layers are adheredtogether with adhesive, binder fibers, thermal bonding, ultrasonicbonding, self-adhesion, or using a combination of such techniques.Preferred methods include the use of an adhesive, binder fibers, or acombination thereof. A particularly preferred method is through the useof an adhesive (pressure sensitive adhesives, hot melt adhesives)applied in a variety of techniques, including, for example, powdercoating, spray coating, or the use of a pre-formed adhesive web.Typically, the adhesive is in a continuous layer, or it can be patternedif so desired as long as the filter medium does not delaminate duringprocessing or use. Exemplary adhesives include hot melt adhesives suchas polyesters, polyamides, acrylates, or combinations thereof (blends orcopolymers).

If an adhesive is used, the amount of adhesive can be readily determinedby one of skill in the art. A desired level is one that providessuitable bonding between the layers without adversely impacting the gasflow through the media. For example, the reduction of the Frazierpermeability of a composite filter medium is preferably less than 20%,or more preferably less than 10%, of the inverse of the sum of theinverse of each layer's permeability (i.e.,(1/A_(perm)+1/B_(perm)+1/C_(perm))⁻¹). This is also applicable for anyother lamination methods.

In order to increase rigidity and provide better flow channel in anelement, a filter medium can be corrugated. Thus, in certainembodiments, filter media of the present disclosure should have thecharacteristics to survive a typical hot corrugation process withoutmedia damage (which often deteriorate the media performance).

With or without the corrugation, a filter medium can be folded intomultiple folds or pleats and then installed in a filter housing orframe. Pleating of a flat sheet or corrugated sheet can be carried outusing any number of pleating techniques, including but not limited to,rotary pleating, blade pleating, and the like. The corrugated media mayhave any one of several pleat supporting mechanisms applied to thepleated media as described in U.S. Pat. No. 5,306,321. For example,corrugated aluminum separators, hot melt beads, and indentations (oftenreferred to as PLEATLOC pleated media) can be used.

In certain embodiments, a fold is imprinted into the filter media in aspacer form so bonding of the folds is prevented in an effective way,even in cases if the media is moist or overloaded. These dents on thepleat tips that are vertical to the corrugation channel direction onboth sides of the media, keep pleats separated, and provide better flowchannels for gas (e.g., air) to flow through the pleat pack in anelement. If in a conical or cylindrical type element, such as that shownin FIGS. 9-14 , dents on the outside can be deeper and wider than thoseon the inside to keep even separation in pleats.

For a noncorrugated media, other pleat separation methods can be used onany of the media described herein, such as those involving the additionof a hot-melt adhesive bead between the pleats, or the use of combseparators. The pleated material can be formed into a cylinder or “tube”and then bonded together, such as through the use of an adhesive (e.g.,a urethane-based, hot-melt adhesive, etc.), or ultrasonic welding (i.e.,ultrasonic bonding), for example.

In certain embodiments, filter layers, composite filter media (flat orcorrugated), and filter elements of the present disclosure are referredto as “high efficiency.” In certain embodiments, a high-efficiencyfilter layer of the present disclosure is able to remove at least 55%,at least 70%, at least 80%, at least 85%, at least 95%, at least 99.5%,at least 99.95%, or at least 99.995% (by number), of 0.4-micron sizeDEHS particles at 4 ft/min (2 cm/sec). In certain embodiments, ahigh-efficiency composite filter medium (which may or may not becorrugated) and/or filter element (which is typically corrugated andpleated) of the present disclosure displays an efficiency of at least F9per EN779:2012. In certain embodiments, a high-efficiency filter element(which is typically corrugated and pleated) of the present disclosuredisplays an efficiency of at least E10, at least E11, or at least E12per EN1822:2009.

In certain embodiments, the filter medium of displays an efficiency ofat least 80%, or greater than 80%, per the DEHS efficiency test at themost penetrating particle size.

In certain embodiments, a filter layer and/or composite filter medium ofthe present disclosure has good depth loading characteristics.

In certain embodiments, a depth loading filter layer has a relativelylow solidity. As used herein, solidity is the solid fiber volume dividedby the total volume of the filter medium at issue, usually expressed asa percentage, or put another way, the volume fraction of media occupiedby the fibers as a ratio of the fibers volume per unit mass divided bythe media's volume per unit mass. A suitable test for determiningsolidity is described in, for example, U.S. Patent Publication No.2014/0260137. Typically, a solidity of less than 20 percent (%) at apressure of 1.5 pounds per square inch (psi) (i.e., 0.1 kg/cm²), oroften less than 15%, is desirable.

In certain embodiments, a filter layer and/or composite filter medium ofthe present disclosure demonstrates high strength and high flexibility.This can be demonstrated by a relatively low loss in tensile strengthafter a layer and/or a composite medium has been folded or corrugated.Less than 20% loss of tensile strength after folding or corrugation of afilter layer or filter medium is desirable.

Surface Loading Filter Layer

A surface loading filter layer is a filter layer that captures asubstantial portion of incident particles at the surface of the layer,as opposed to the volume or thickness of the filter layer (i.e., in the“z” direction). That is, a surface loading filter layer can stopincident particulate from passing through the surface loading filterlayer and can attain substantial surface loadings of trapped particles.

A surface loading filter layer of filter media of the present disclosureincludes fine fibers having an average fiber diameter of less than 1micron (i.e., 1000 nanometers), or up to 0.5 micron, or up to 0.3micron. This includes nanofibers and microfibers. Nanofiber is a fiberwith diameter less than 200 nanometers or 0.2 micron. Microfiber is afiber with diameter larger than 0.2 micron, but not larger than 10microns. In certain embodiments, the fine fibers have an averagediameter of at least 0.01 micron, or at least 0.05 micron, or at least0.1 micron.

In certain embodiments, the surface loading filter layer has a basisweight of less than 1 gram per square meter (g/m² or gsm). In certainembodiments, the surface loading filter layer has a basis weight of atleast 0.0001 g/m².

In certain embodiments, the surface loading filter layer has a LEFSfiltration efficiency of at least 30%, at least 40%, at least 50%, atleast 60%, at least 70%, or at least 80%. In certain embodiments, thefine fiber filter layer has a LEFS filtration efficiency of up to 99%,up to 98%, up to 97%, up to 96%, up to 95%, up to 94%, up to 93%, up to92%, up to 91%, or up to 90%.

Examples of fine fibers are disclosed in U.S. Pat. No. 8,118,901.

A surface loading filter layer of the disclosure may include a randomdistribution of fine fibers which can be bonded to form an interlockingnet. Filtration performance is obtained largely as a result of the finefiber barrier to the passage of particulate. Structural properties ofstiffness, strength, pleatability are typically provided by a supportlayer included within the filter media (e.g., a support layer to whichthe fine fibers are adhered).

In certain embodiments, a surface loading filter layer may include finefiber interlocking networks. Such networks typically include fine fibersin the form of microfibers or nanofibers and relatively small spacesbetween the fibers. Such spaces typically range, between fibers, of 0.01micron to 25 microns or often 0.1 micron to 10 microns.

In certain embodiments, the fine fiber adds less than 1 micron inthickness to the overall filter media. In service, the filters can stopincident particulate from passing through the surface loading filterlayer and can attain substantial surface loadings of trapped particles.The particles comprising dust or other incident particulates rapidlyform a dust cake on the fine fiber surface and maintain high initial andoverall efficiency of particulate removal. Even with relatively finecontaminants having a particle size of 0.01 micron to 1 micron, thefilter media comprising the fine fibers has a very high dust capacity.

Suitable polymer materials useful for making the fine fibers havesubstantially improved resistance to the undesirable effects of heat,humidity, high flow rates, reverse pulse cleaning, operational abrasion,submicron particulates, cleaning of filters in use and other demandingconditions.

Examples of fine fibers and the polymer materials of which they are madeare disclosed in U.S. Pat. No. 8,118,901. Such polymer materials includeboth addition polymer and condensation polymer materials such aspolyolefin, polyacetal, polyamide, polyester, cellulose ether and ester,polyalkylene sulfide, polyarylene oxide, polysulfone, modifiedpolysulfone polymers and mixtures thereof. Preferred materials that fallwithin these generic classes include polyethylene, polypropylene,poly(vinylchloride), polymethylmethacrylate (and other acrylic resins),polystyrene, and copolymers thereof (including ABA type blockcopolymers), poly(vinylidene fluoride), poly(vinylidene chloride),polyvinylalcohol in various degrees of hydrolysis (87% to 99.5%) incrosslinked and non-crosslinked forms. Preferred addition polymers tendto be glassy (a Tg greater than room temperature). This is the case forpolyvinylchloride and polymethylmethacrylate, polystyrene polymercompositions or alloys thereof, or for polyvinylidene fluoride andpolyvinylalcohol materials.

One class of polyamide condensation polymers are nylon materials. Theterm “nylon” is a generic name for all long chain synthetic polyamides.Typically, nylon nomenclature includes a series of numbers such as innylon-6,6 which indicates that the starting materials are a C₆ diamineand a C₆ diacid (the first digit indicating a C₆ diamine and the seconddigit indicating a C₆ dicarboxylic acid compound). Another nylon can bemade by the polycondensation of epsilon caprolactam in the presence of asmall amount of water. This reaction forms a nylon-6 (made from a cycliclactam—also known as episilon-aminocaproic acid) that is a linearpolyamide. Further, nylon copolymers are also contemplated.

Copolymers can be made by combining various diamine compounds, variousdiacid compounds and various cyclic lactam structures in a reactionmixture and then forming the nylon with randomly positioned monomericmaterials in a polyamide structure. For example, a nylon 6,6-6,10material is a nylon manufactured from hexamethylene diamine and a C₆ anda C₁₀ blend of diacids. A nylon 6-6,6-6,10 is a nylon manufactured bycopolymerization of epsilonaminocaproic acid, hexamethylene diamine anda blend of a C₆ and a C₁₀ diacid material.

Block copolymers are also useful in making the fine fibers. With suchcopolymers the choice of solvent swelling agent is important. Theselected solvent is such that both blocks were soluble in the solvent.One example is an ABA (styrene-EP-styrene) or AB (styrene-EP) polymer inmethylene chloride solvent. If one component is not soluble in thesolvent, it will form a gel. Examples of such block copolymers areKRATON copolymers of styrene-b-butadiene and styrene-b-hydrogenatedbutadiene (ethylene propylene), PEBAX copolymers ofe-caprolactam-b-ethylene oxide, SYMPATEX polyester-b-ethylene oxide andpolyurethanes of ethylene oxide and isocyanates.

Addition polymers like polyvinylidene fluoride, syndiotacticpolystyrene, copolymer of vinylidene fluoride and hexafluoropropylene,polyvinyl alcohol, polyvinyl acetate, amorphous addition polymers, suchas poly(acrylonitrile) and its copolymers with acrylic acid andmethacrylates, polystyrene, poly(vinyl chloride) and its variouscopolymers, poly(methyl methacrylate) and its various copolymers, can besolution spun with relative ease because they are soluble at lowpressures and temperatures. However, highly crystalline polymer likepolyethylene and polypropylene require high temperature, high pressuresolvent if they are to be solution spun. Therefore, solution spinning ofthe polyethylene and polypropylene is very difficult. Electrostaticsolution spinning is one method of making fine fibers.

In certain embodiments, fine fibers include a single polymeric material.In certain embodiments, fine fibers include a polymer mixture thatincludes a first polymer and a second, but different polymer (differingin polymer type, molecular weight or physical property) that isconditioned or treated at elevated temperature. The polymer mixture canbe reacted and formed into a single chemical species or can bephysically combined into a blended composition by an annealing process.Annealing implies a physical change, like crystallinity, stressrelaxation or orientation. In certain embodiments, polymer materials arechemically reacted into a single polymeric species such that aDifferential Scanning Calorimeter analysis reveals a single polymericmaterial. Mixtures of similar polymers such as a compatible mixture ofsimilar nylons, similar polyvinylchloride polymers, blends ofpolyvinylidene chloride polymers are useful in the fibers of the surfaceloading filter layer.

In certain embodiments, the fine fibers include nylon, polyvinylidenefluoride, polyurethane, or combinations (e.g., blends or copolymers)thereof.

Additive materials can also be used to form a surface coating on thefine fibers that provides oleophobicity, hydrophobicity, or otherassociated improved stability when contacted with high temperature, highhumidity, and difficult operating conditions. Such fine fibers can havea smooth surface including a discrete layer of the additive material oran outer coating of the additive material that is partly solubilized oralloyed in the polymer surface, or both.

Additives include a fluoro-surfactant, a nonionic surfactant, lowmolecular weight resins, e.g., a tertiary butylphenol resin having amolecular weight of less than about 3000. The resin is characterized byoligomeric bonding between phenol nuclei in the absence of methylenebridging groups. The positions of the hydroxyl and the tertiary butylgroup can be randomly positioned around the rings. Bonding betweenphenolic nuclei always occurs next to hydroxyl group, not randomly.Similarly, the polymeric material can be combined with an alcoholsoluble non-linear polymerized resin formed from bis-phenol A. Suchmaterial is similar to the tertiary butylphenol resin described above inthat it is formed using oligomeric bonds that directly connect aromaticring to aromatic ring in the absence of any bridging groups such asalkylene or methylene groups.

In certain embodiments, the polymers and optional additives are selectedto provide temperature resistance, humidity or moisture resistance, andsolvent resistance. In certain embodiments, the polymer material andoptional additives are selected to survive intact various operatingtemperatures, i.e., a temperature of 140° F., 160° F., 270° F., 300° F.for a period of time of 1 hour or 3 hours, depending on end use, whileretaining 30%, 50%, 80%, or 90% of filter efficiency or of effectivefine fibers in a filter layer. Survival at these temperatures isimportant at low humidity, high humidity, and in water saturated gas(e.g., air).

In certain embodiments, the polymers and optional additives are selectedto provide adhesion of the material to the remainder of the mediastructure such that the composite media can be processed into a filterstructure including pleats, rolled materials, and other structureswithout significant delamination.

A fine fiber filter layer may include a bi-layer or multi-layerstructure wherein the filter contains one or more surface loading filterlayers combined with or separated by one or more synthetic, cellulosic,or blended webs. Another preferred motif is a structure including finefiber in a matrix or blend of other fibers.

For pulse cleaning application, an extremely thin layer of fine fiberscan help to minimize pressure loss and provide an outer surface forparticle capture and release. A thin layer of fibers of less than 1micron diameter, or less than 0.5-micron diameter is preferred forself-cleaning applications. Good adhesion between the fine fibers andthe adjacent layer (e.g., depth loading layer) is important. Selfcleaning the surface by back pulsing repeatedly rejuvenates the filtermedium. As a great force is exerted on the surface, fine fiber with pooradhesion to substrates can delaminate upon a back pulse that passes fromthe interior of a filter through a substrate to the surface loadingfilter layer.

Depth Loading Layer

A depth loading layer is a filter layer that captures particlesthroughout the volume of the layer. As such, dirt is captured throughoutthe thickness of the filter layer (i.e., in the “z” direction) asopposed to on the surface of a surface loading filter layer.

A depth loading layer is often characterized in terms of its porosity,density, and solids content percentage. For example, a 5% solidity mediameans that about 5% of the overall volume comprises solids (e.g.,fibrous materials) and the remainder is void space that is filled by airor other fluid.

In certain embodiments, a depth loading filter layer has a relativelylow solidity. Typically, a depth loading filter layer has a solidity ofless than 20 percent (%) at a pressure of 1.5 psi (i.e., 0.1 kg/cm²),often less than 15%. In certain embodiments, a depth loading filterlayer of the present disclosure has a solidity of at least 5 percent ata pressure of 1.5 psi (i.e., 0.1 kg/cm²).

In certain embodiments, a depth loading filter layer has a Frazierpermeability (differential pressure set at 0.5 inch of water) of atleast 8 liters per square meter per second (l/m²/sec), at least20l/m²/sec, at least 40l/m²/sec, at least 80l/m²/sec, at least100l/m²/sec, or at least 200l/m²/sec, when evaluated separately from theremainder of the construction. In certain embodiments, a depth loadingfilter layer has a Frazier permeability (differential pressure set at0.5 inch of water) of up to 1000l/m²-sec, up to 800l/m²-sec, up to600l/m²-sec, up to 400l/m²-sec, or up to 200l/m²/sec, when evaluatedseparately from the remainder of the construction.

Another commonly used depth loading filter layer characteristic is fiberdiameter. Generally smaller diameter fibers for a given soliditypercentage will cause the filter media to become more efficient with theability to trap smaller particles. Smaller fibers can be packed togetherin greater numbers without increasing the overall solidity percentage,given the fact that smaller fibers take up less volume than largerfibers.

Because a depth loading filter layer traps particulates substantiallythroughout the volume or depth, such filter layer can be loaded with ahigher weight and volume of particulates as compared to surface loadingfilter layers over the lifespan of the filter media. Depth loadingfilter layers, however, tend to have lower efficiencies than surfaceloading filter layers. To facilitate such high loading capacity, alow-solidity depth loading filter layer is often chosen for use. Thismay result in a large average pore size, which has the potential toallow some particulates to pass more readily through the filter.Gradient density systems and/or adding a surface loading filter layercan provide for improved efficiency characteristics.

In certain embodiments, a depth loading layer of the filter media of thepresent disclosure is a high-efficiency filter layer. In certainembodiments, a high-efficiency filter layer displays a filtrationefficiency of at least 55%, or at least 70% with 0.4-micron size DEHS(di-ethyl-hexyl-sebacat) particles at 4 ft/min (2 cm/sec). Preferably,the filtration efficiency is at least at least 80%, at least 85%, atleast 95%, at least 99.5%, at least 99.95%, or at least 99.995% of themost penetrating particle size (MPPS) particles at 4 ft/min (2 cm/sec).

In certain embodiments, a depth loading layer displays a filtrationefficiency of up to 99%, up to 99.5%, up to 99.97%, or up to 99.997%,with 0.4-micron size DEHS (di-ethyl-hexyl-sebacat) particles at 4 ft/min(2 cm/sec).

In certain embodiments, a depth loading filter layer of the presentdisclosure displays a salt loading capacity of at least 1 gram persquare meter (g/m² or gsm), at least 2 g/m², at least 3 g/m², at least 4g/m², at least 5 g/m², at least 6 g/m², at least 7 g/m², at least 8g/m², at least 9 g/m², or at least 10 g/m², at a terminal pressure dropof 2 inches water column rise over initial (i.e., 500 Pa). Typically,the higher salt loading capacity the better, as this is an indicator oflife of the product. In certain embodiments, a depth loading filterlayer displays a salt loading capacity of up to 10 g/m² at 500 Pascalspressure rise over initial.

In certain embodiments, a depth loading layer is at least 0.005 inch(125 microns) thick, and often at least 0.01 inch (250 microns) thick.In certain embodiments, a depth loading layer is up to 0.02 inch (500microns) thick.

In certain embodiments, a depth loading filter layer has a basis weightof at least 10 g/m², at least 20 g/m², at least 30 g/m², at least 40g/m², or at least 50 g/m². In certain embodiments, a depth loadingfilter layer has a basis weight of up to 150 g/m², up to 140 g/m², up to130 g/m², up to 120 g/m², up to 110 g/m², up to 100 g/m².

In certain embodiments, the depth loading layer displays a dust loadingcapacity of at least 0.5 g/ft² (5.4 g/m²) at 2 inches water pressurerise and 10 ft/min (5.8 cm/sec) with 0.3 micron NaCl particles. Incertain embodiments, the depth loading layer displays a dust loadingcapacity of up to 5 g/ft² (53.8 g/m²) at 2 inches water pressure riseand 10 ft/m in (5.8 cm/sec) with 0.3 micron NaCl particles.

In certain embodiments, a depth loading layer includes aglass-containing filter layer, a melt-blown filter layer, or acombination thereof.

In certain embodiments, a depth loading layer includes aglass-containing filter layer. In certain embodiments of aglass-containing filter layer, such layer includes glass fibers havingan average diameter of up to 2 microns, up to 1 micron, or up to 0.5micron. In certain embodiments, the glass fibers have an averagediameter of at least 0.01 micron, at least 0.05, at least 0.1 micron, atleast 0.2 micron, at least 0.3 micron, or at least 0.4 micron.

A glass-containing filter layer may also include fibers other than theglass-containing fibers. For example, it may contain multi-componentfibers, typically bicomponent fibers, that function as binder fibers. Apreferred example is bicomponent binder fibers that are core-sheathfibers having a low melting point polyester sheath and a higher meltingpoint polyester core. Bicomponent fibers typically have fiber diametersof at least 10 microns.

A glass-containing filter layer may also include polyester fibersdistinct from the multi-component fibers. Preferred glass-containingfilter layers of the present disclosure include only glass fibers andbicomponent binder fibers. In certain embodiments, the polyester fibersdistinct from the multi-component binder fibers have an average diameterof 10 microns to 14 microns.

Fibers of the glass-containing filter layer may be made by a variety ofprocesses. In certain embodiments, the glass-containing filter layer iscreated using a wet-laid process.

Although the binder fibers in the glass-containing filter layer are usedto avoid the use of any binder resin, such resin can be added to furtherimprove its strength. Examples of suitable binder resins includesolvent-based or water-based latex resins, water-based styrene acrylics,solvent-based phenolics, and solvent-based non-phenolics, such as thatavailable under the tradename HYCAR 26138 from Lubrizol of Cleveland, OHTypically, if used, a binder resin could be present in theglass-containing filter layer in an amount of up to 10 wt-%, up to 5wt-%, or up to 1 wt-%, based on the total weight of the glass-containingfilter layer. Preferably, no binder resin is used in theglass-containing filter layer (or in any of the layers of the filtermedia).

Examples of suitable glass-containing filter layers include thosedescribed in U.S. Pat. Nos. 7,309,372, 7,314,497, 7,985,344, 8,057,567,and 8,268,033, and U.S. Publication Nos. 2006/0242933 and 2008/0245037.

In certain embodiments, a depth loading layer includes a melt-blownfilter layer. Typically, melt-blowing is a nonwoven web forming processthat extrudes and draws molten polymer resins with heated, high velocitygas (e.g., air) to form fine filaments. The filaments are cooled andcollected as a web onto a moving screen. The process is similar to thespunbond process, but melt-blown fibers are typically much finer.

Typically, the melt-blown fibers have an average diameter of no greaterthan 20 microns. In certain embodiments, the melt-blown filter layerincludes melt-blown fibers having an average diameter of up to 10microns, up to 5 microns, up to 4 microns, or up to 3 microns. Incertain embodiments, the melt-blown filter layer includes melt-blownfibers having an average diameter of at least 0.5 micron, at least 1micron, at least 1.5 microns, or at least 2 microns. In certainembodiments, the melt-blown fibers have an average diameter of 2-3microns.

In certain embodiments, scaffold fibers as described in InternationalPublication No. WO 2013/025445 can be included in the melt-blown filterlayer if desired for enhancing performance. However, media with highlevels of compressibility have little or no scaffold fibers used asdescribed in International Publication No. WO 2013/025445 in themelt-blown filter layer. The scaffold fibers provide support for themedia fiber, and add improved handling, greater tensile strength, andresults in lower compressibility to the media.

In certain embodiments, the melt-blown filter layer includes acontinuously gradient structure of larger fibers and more open structureat a first major surface and smaller fibers and less open structure at asecond major surface. In certain embodiments of this construction, thesecond major surface of the melt-blown filter layer is adjacent thesupport layer and the first major surface is positioned as the mostupstream surface (i.e., the first layer encountered by the gas (e.g.,air) stream during use).

In certain embodiments, a melt-blown filter layer includes a compositeof multiple layers of melt-blown fibers with larger fibers and more openstructure at a first major surface of the melt-blown composite andsmaller fibers and less open structure at a second major surface of themelt-blown composite. In certain embodiments of this construction, thesecond major surface of the melt-blown filter layer is adjacent thesupport layer and the first major surface is positioned adjacent thesurface loading filter layer.

In certain embodiments, melt-blown fibers can be prepared from a varietyof polymers that are suitable for being melt blown. Examples includepolyolefins (particularly polypropylene),ethylene-chloro-trifluoro-ethylene, other hydrophobic polymers, ornon-hydrophobic polymers (e.g., polybutylene terephthalate, polystyrene,polylactic acid, polycarbonate, nylon, polyphenylene sulfide) with ahydrophobic coating or additive, or combinations thereof (e.g., blendsor copolymers). Preferred polymers are polyolefins such aspolypropylene, polyethylene, and polybutylene.

In certain embodiments, a melt-blown filter layer includes fibers madefrom polypropylene, polybutylene terephthalate, or combinations thereof.Particularly preferred melt-blown fibers are made from polypropylene toenhance the watertight characteristics of a preferred filter medium ofthe present disclosure.

In certain embodiments, the melt-blown filter layer is hydrophobic. Bythis it is meant that the layer demonstrates a contact angle greaterthan 90 degrees with water. The fibrous material of which it is made canbe hydrophobic (e.g., a polyolefin) or include a hydrophobic additive,or be coated with a hydrophobic material. Similarly, in certainembodiments, to enhance watertight characteristics, the glass-containingfilter layer is coated with a hydrophobic coating. Alternatively, adepth loading filter layer can be treated with a plasma treatmenttechnique.

Suitable hydrophobic materials have little or no affinity for water, orcompletely repel water, and thereby prevent or restrict water frompassing through the filter media. Typically, the hydrophobic materialdemonstrates a contact angle greater than 90 degrees when tested withwater. Examples of hydrophobic materials include fluorochemicals,particularly fluoropolymers as described in U.S. Pat. No. 6,196,708.

Examples of useful fluoropolymers include those having a fluoroalkylportion or, preferably, a perfluoroalkyl portion. These fluoropolymersinclude, for example, fluoroalkyl esters, fluoroalkyl ethers,fluoroalkyl amides, and fluoroalkyl urethanes. Often, the fluoroalkyland/or perfluoroalkyl portion extends from a backbone of the polymer.

The fluoropolymers may include a variety of monomer units. Exemplarymonomer units include, for example, fluoroalkyl acrylates, fluoroalkylmethacrylates, fluoroalkyl aryl urethanes, fluoroalkyl allyl urethanes,fluoroalkyl maleic acid esters, fluoroalkyl urethane acrylates,fluoroalkyl amides, fluoroalkyl sulfonamide acrylates and the like. Thefluoropolymers may optionally have additional non-fluoro monomer unitsincluding, for example, unsaturated hydrocarbons (e.g., olefins),acrylates, and methacrylates. Additional examples of suitablefluoropolymers are provided in U.S. Pat. No. 3,341,497.

Commercially available fluoropolymers include those available under thetrade designation OLEOPHOBOL CPX from Huntsman (Charlotte, NC), as wellas 3M Protective Material PM-490 (a nonionic fluorochemical resin), 3MProtective Material PM-3633 (a fluoropolymer emulsion), 3M L-21484 (afluorinated amino salt derivative that can be diluted in water or polarorganic solvents), all of which are available from 3M Co. (St. Paul,MN).

Other exemplary, commercially available fluoropolymers are provided inaqueous emulsions. The fluoropolymers can be extracted from the aqueousemulsion by removal of the water carrier. The fluoropolymers can then besolvated in an organic solvent. To facilitate the solvation of thefluoropolymer, a compound, such as acetone, can be optionally added tothe aqueous emulsion to break the emulsion. In addition, the particlesof fluoropolymer can be optionally ground, subsequent to removal ofwater to make solvation easier and quicker.

Methods of coating such material are conventional and well known tothose skilled in the art. A typical coating weight is at least 0.5 wt-%and often no more than 3 wt-%.

Support Layer

Filter media of the present disclosure includes a support layer. Thesupport layer can be of any of a variety of porous materials, includingfibrous materials, metal mesh, etc. Typically, fibrous materials usedfor the support layer are made of natural fiber and/or synthetic fibers.It could be woven or nonwoven. It could be spunbond, wet-laid, etc.

In certain embodiments, the support layer includes fibers having anaverage diameter of at least 5 microns, or at least 10 microns. Incertain embodiments, the support layer can include fibers having anaverage diameter of up to 250 microns.

In certain embodiments, the support layer has a basis weight of at least50 grams/meter² (g/m² or gsm), or at least 100 gsm. In certainembodiments, the support layer has a basis weight of up to 260grams/meter² (g/m² or gsm), up to 200 g/m², or up to 150 g/m².

In certain embodiments, the support layer is at least 0.005 inch (125microns) thick, and often at least 0.01 inch (250 microns) thick. Incertain embodiments, the support layer is up to 0.03 inch (750 microns)thick.

In certain embodiments, the support layer has an air permeability of atleast 10 cubic feet per minute (ft³/min) ( ) at 125 Pa (80.2 l/m²/sec at200 Pa), when evaluated separately from the remainder of theconstruction. In certain embodiments, an air permeability of up to 1000cubic feet per minute (ft³/min) at 125 Pa (8020l/m²/s at 200 Pa), whenevaluated separately from the remainder of the construction.

In certain embodiments, the support layer has a Gurley stiffness of atleast 1000 milligrams, and often at least 5000 milligrams. In certainembodiments, the support layer can have a Gurley stiffness of up to10,000 milligrams. A method for measuring Gurley stiffness is describedin TAPPI No. T543.

Examples of suitable material for the support layer (i.e., substrate)include spunbond, wet-laid, carded, or melt-blown nonwoven. Suitablefibers can be cellulosic fiber, glass fibers, metal fibers, or syntheticpolymeric fibers or the combination. Fibers can be in the form of wovensor nonwovens. Plastic or metal screen-like materials both extruded andhole punched, are other examples of filter substrates. Examples ofsynthetic nonwovens include polyester nonwovens, nylon nonwovens,polyolefin (e.g., polypropylene) nonwovens, polycarbonate nonwovens, orblended or multicomponent nonwovens thereof. Sheet-like substrates(e.g., cellulosic, synthetic, and/or glass or combination webs) aretypical examples of filter substrates. Other preferred examples ofsuitable substrates include polyester or bicomponent polyester fibers(as described herein for the glass-containing filter layer) orpolypropylene/polyethylene terephthalate, or polyethylene/polyethyleneterephthalate bicomponent fibers in a spunbond.

In certain embodiments, the support layer includes wet-laid fibers. Incertain embodiments, the support layer includes wet-laid cellulosefibers, polyester fibers, or a combination thereof.

In certain embodiments, the support layer is hydrophobic. The fibrousmaterial of which it is made can be hydrophobic (e.g., a polyolefin) orinclude a hydrophobic additive, or it can be coated with a hydrophobicmaterial, such as the ones described herein for the hydrophobic coatingon the glass-containing filter layer, or it can be treated with a plasmatreatment technique. Alternatively, if wet-laid, a hydrophobic resin canbe applied during the wet-laid process.

Optional Scrim Layer

In certain embodiments, a scrim layer can be used to enhance thestiffness of filter media of the present disclosure. Typically, a scrimlayer is disposed between the surface loading filter layer and the depthloading filter layer. Useful materials for the scrim layer typicallyhave a high permeability (i.e., “perm”) (e.g., greater than 1600l/m²/s)and are thin (e.g., less than 0.005 inch) so there is a minimal effecton the flat sheet or filter element performance. Examples of such scrimmaterials include those available under the tradenames FINON C303NW andFINON C3019 NW from Midwest Filtration in Cincinnati, OH. Others aredescribed, for example, in U.S. Pat. Pub. 2009/0120868.

Filter Elements and Uses

The filter media of the present disclosure can then be manufactured intofilter elements (i.e., filtration elements), including, e.g., flat-panelfilters, cartridge filters, or other filtration components (e.g.,cylindrical or conical). Examples of such filter elements are describedin U.S. Pat. Nos. 6,746,517; 6,673,136; 6,800,117; 6,875,256; 6,716,274;and 7,316,723, as well as U.S. Patent Application No. 2014/0260142.

The filter media can be corrugated. Exemplary corrugations are at adepth of 0.020 to 0.035 inch (0.5 mm to 0.9 mm). Corrugated filter mediacan then typically be pleated to form a pleat pack, then placed andsealed into a housing, as is known in the art.

Filter elements of the present disclosure can be used in industrialfiltration such as in dust collectors, and in commercial and residentialHVAC systems.

FIGS. 4-14 depict various embodiments of filter elements of the presentdisclosure that are usable in gas turbine air intake systems orindustrial air cleaners.

In FIG. 4 , a pleated panel element 200 is shown in perspective view.The panel element 200 includes a media pack 202 of pleated media 204.The pleated media 204 can include a filter medium described herein. Inthe embodiment shown, the media pack 202 is held within a frame 206,with the examples shown being a rectangular frame 206. The frame 206typically will include a gasket (not shown) for permitting the element200 to be sealed against a tube sheet in the intake system. In FIG. 4 ,the upstream side of the pleated media 204 with the surface loadingfilter layer is shown at 205 on the same side as the incoming gas (e.g.,air) shown at arrow 207. The cleaned gas (e.g., air) is shown at arrow208, and emerges from the media 204 from a downstream side of the media.

FIG. 5 depicts a perspective view of pocket filter element 210. Thepocket element 210 includes a layer of filter media 212 that cancomprise a filter medium of the present disclosure. In the embodimentshown, the pocket element 210 includes a plurality of panel pairs 213,214, with each panel pair 213, 214 forming a V-like shape. The filtermedia 212 is secured to a frame 216. The frame 216 typically will carrya gasket for allowing the pocket element 210 to be sealed against a tubesheet. In such an arrangement, the media 212 has an upstream melt-blownside 217, which is inside of the V's, and a downstream side 218, whichis on the outside of the V's.

FIGS. 6-8 depict views of a mini-pleat or multi-V style element 220. Theelement 220 includes a frame 222 holding a filter media pack 224 (FIG. 8). The media pack 224 comprises a plurality of mini-pleats. Themini-pleats are arranged in a panel 226, and the element 220 includes aplurality of mini-pleated panel pairs 227, 228 (FIG. 6 ) of the media ofthe invention, each forming a V-like shape. In FIG. 6 , the panel pairs227, 228 are shown in hidden lines, since the top portion of the frame222 obstructs the view of the panel pairs 227, 228. The frame 222defines a plurality of dirty gas (e.g., air) inlets 229 (FIG. 7 ), whichleads to the inside part of each V of each pleated panel pair 227, 228.Each pleated panel pair 227, 228 includes an upstream side 230, which ison the inside of the V, and a downstream side 231, which is on theoutside of the V.

FIGS. 9-14 show various embodiments of tubular, pleated filter elements.FIG. 9 shows a cylindrical pleated element 240 having a media pack 242that can include a filter medium of the present disclosure with anupstream side 244 and a downstream side 246. The downstream side 246 isinside of the interior volume of the element 240.

FIG. 10 depicts two of the cylindrical elements 240 axially aligned,such that they are stacked end to end.

In FIG. 11 , cylindrical element 240 is axially aligned with a partiallyconical element 250. The partially conical element 250 is a tubularelement having a media pack 252 that can include a filter medium of thepresent disclosure. The element has an upstream side 254 and adownstream side 256. The conical element 250 has a first end 258 havinga diameter that matches the diameter of the cylindrical element 240. Theconical element 250 includes a second end 260 having a diameter that islarger than the diameter of the first end 258, thus forming the partialcone.

FIG. 12 depicts two partially conical elements 270, 280 arrangedaxially, and engaged end to end. Each of the elements 270 includes amedia pack 272, 282 forming a tube that can include a filter medium ofthe present disclosure. The media packs 272, 282 each have an upstreamside 274, 284 and a downstream side 276, 286.

FIG. 13 shows a single conical element 270. The element 270 can be usedalone installed in the intake system for a gas turbine without beinginstalled in element pairs, as shown in FIGS. 11 and 12 .

FIG. 14 is another embodiment of a filter element 290 having media pack292 that can include a filter medium of the present disclosure. Themedia pack 292 is pleated and forms a tubular shape. In this embodiment,the tubular shape is an oval shape, and in one example embodiment, aratio of the short axis compared to the long axis of the oval is about0.7-0.9. The media 292 includes an upstream side 294 and a downstreamside 296.

FIG. 15 is another embodiment of a filter element, in the form of anovate structure, that can include a filter medium of the presentdisclosure. The filter element includes filter media 310 having end caps320 located on each of the first end 312 and the second end 314 of thefilter media 310. The end cap 320 on first end 312 of the filter media310 may have an opening that allows access to the interior volume offilter cartridge. The end cap 320 on the opposite end of the filtermedia 310 may be closed so that it prevents access to the interiorvolume of the filter cartridge and so that gas (e.g., air) entering theinterior volume of the filter cartridge through the end cap 320 on thefirst end 312 of the filter media 310 must exit through the filter mediain the filter element.

Referring to FIG. 15 , in one or more alternative embodiments, both endcaps 320 may be open to allow access to the interior volume of thefilter element. In one or more embodiments, a gasket 322 may be providedon the end cap 320 to seal the filter cartridge over an opening in,e.g., a tubesheet, a venturi, or other structure through which gas isdelivered into the interior volume of the filter element. A tube axis311 extends through the tubular filter cartridge between the first end312 and the second end 314. The filter media 310 in the filtercartridges described herein defines an exterior surface 316 and interiorsurface 318 located around the tube axis 311. The interior surface 318faces an interior volume of the filter cartridge 310 and the exteriorsurface 316 faces away from that interior volume.

In the filter element of FIG. 15 the end caps 320 may include analignment mechanism in the form of, e.g., optional tabs 324 in whichnotches 326 are located. The notches 326 may be sized to receive upperand lower members 352 and 354 of a yoke 350 over which the filtercartridge may be mounted in a filter system. Each of the notches 326 maybe described as having, in one or more embodiments, an opening thatfaces the interior volume of the filter cartridges, with the notch 326extending towards the inner perimeter 328 of the end cap 320. Althougheach notch 326 is formed in a single tab 324 in the depicted embodiment,in one or more alternative embodiments, a notch 326 may be formedbetween two members that protrude from the inner perimeter 328 of theend cap 320 where the two members forming the notch 326 are not the samestructural member. The use of two tabs 324 in combination with a yoke350 having two members 352 and 354 may be beneficial to prevent, or atleast limit, rotation of a filter cartridge about its tube axis 311 wheninstalled on the yoke 350 in a filter system. Such filter element isdescribed in further details in U.S. Patent Publication No.2014/0260142.

It should be understood that each of the filter elements characterizedabove and depicted in FIGS. 4-15 can be flat media or corrugated mediaand/or operably installed in an intake system for a gas turbine or otherventilation system.

In operation, gas (e.g., air) to be filtered will be directed throughthe upstream side, the surface loading fine fiber filter layer and thenthrough the downstream side of filter media in the respective filterelement typically installed in a tube sheet. The filter media willremove at least some of the particulate from the gas (e.g., air) stream.After passing through the downstream side of the media, the filtered gas(e.g., air) is then directed to the gas turbine.

EXEMPLARY EMBODIMENTS

Embodiment 1 is a gas filter medium comprising: a surface loading filterlayer comprising fine fibers having an average diameter of less than 1micron; a depth loading filter layer; and a support layer; wherein thelayers are configured and arranged for placement in a gas stream withthe surface loading filter layer being the most upstream layer.

Embodiment 2 is the filter medium of embodiment 1 which is pulsecleanable.

Embodiment 3 is the filter medium of embodiment 1 or 2 wherein the depthloading filter layer is positioned between the surface loading layer andthe support layer.

Embodiment 4 is the filter medium of any one of embodiments 1 through 3wherein the fine fibers have an average diameter of up to 0.5 micron.

Embodiment 5 is the filter medium of embodiment 4 wherein the finefibers have an average diameter of up to 0.3 micron.

Embodiment 6 is the filter medium of any one of embodiments 1 through 5wherein the fine fibers have an average diameter of at least 0.01micron.

Embodiment 7 is the filter medium of embodiment 6 wherein the finefibers have an average diameter of at least 0.1 micron.

Embodiment 8 is the filter medium of any one of embodiments 1 through 7wherein the fine fibers comprise nylon, polyvinylidene fluoride,polyurethane, or combinations thereof.

Embodiment 9 is the filter medium of any one of embodiments 1 through 8wherein the surface loading filter layer has a LEFS filtrationefficiency of at least 30%.

Embodiment 10 is the filter medium of embodiment 9 wherein the surfaceloading filter layer has a LEFS filtration efficiency of at least 70%.

Embodiment 11 is the filter medium of embodiment 10 wherein the surfaceloading filter layer has a LEFS filtration efficiency of at least 80%.

Embodiment 12 is the filter medium of any one of embodiments 1 through11 wherein the surface loading filter layer has a LEFS filtrationefficiency of up to 99%.

Embodiment 13 is the filter medium of embodiment 12 wherein the surfaceloading filter layer has a LEFS filtration efficiency of up to 95%.

Embodiment 14 is the filter medium of embodiment 13 wherein the surfaceloading filter layer has a LEFS filtration efficiency of up to 90%.

Embodiment 15 is the filter medium of any one of embodiments 1 through14 wherein the depth loading filter layer comprises a high-efficiencyglass-containing filter layer, a high-efficiency melt-blown filterlayer, or a combination thereof.

Embodiment 16 is the filter medium of embodiment 15 wherein the depthloading filter layer comprises a high-efficiency glass-containing filterlayer comprising glass fibers and multi-component binder fibers.

Embodiment 17 is the filter medium of embodiment 16 wherein thehigh-efficiency glass-containing layer comprises up to 10 wt-% of abinder resin, based on the total weight of the glass-containing layer.

Embodiment 18 is the filter medium of embodiment 16 or 17 wherein themulti-component binder fibers of the high-efficiency glass-containingfilter layer comprise bicomponent fibers having a low melting pointpolyester sheath and a higher melting point polyester core.

Embodiment 19 is the filter medium of any one of embodiments 16 through18 wherein the high-efficiency glass-containing filter layer furthercomprises polyester fibers distinct from the multi-component binderfibers.

Embodiment 20 is the filter medium of embodiment 19 wherein thepolyester fibers distinct from the multi-component binder fibers have anaverage diameter of 10 microns to 14 microns.

Embodiment 21 is the filter medium of any one of embodiments 16 through20 wherein the high-efficiency glass-containing filter layer comprisesglass fibers having an average diameter of 0.4 micron to 0.5 micron.

Embodiment 22 is the filter medium of embodiment 15 wherein the depthloading filter layer comprises a high-efficiency melt-blown filterlayer.

Embodiment 23 is the filter medium of embodiment 22 wherein thehigh-efficiency melt-blown filter layer comprises melt-blown fiberscomprising polypropylene, polybutylene terephthalate, or combinationsthereof.

Embodiment 24 is the filter medium of embodiment 22 or 23 wherein thehigh-efficiency melt-blown filter layer comprises melt-blown fibershaving an average diameter of 0.5 micron to 10 microns.

Embodiment 25 is the filter medium of embodiment 24 wherein thehigh-efficiency melt-blown filter layer comprises melt-blown fibershaving an average diameter of 0.5 micron to 4 microns.

Embodiment 26 is the filter medium of embodiment 25 wherein thehigh-efficiency melt-blown filter layer comprises melt-blown fibershaving an average diameter of 1 micron to 3 microns.

Embodiment 27 is the filter medium of embodiment 25 wherein thehigh-efficiency melt-blown filter layer comprises melt-blown fibershaving an average diameter of 2 microns to 3 microns.

Embodiment 28 is the filter medium of any one of embodiments 1 through27 wherein the depth loading filter layer displays a DEHS filtrationefficiency of at least 55%.

Embodiment 29 is the filter medium of embodiment 28 wherein the depthloading filter layer displays a DEHS filtration efficiency of at least70%.

Embodiment 30 is the filter medium of any one of embodiments 1 through29 wherein the depth loading filter layer displays a DEHS filtrationefficiency of up to 99.997%.

Embodiment 31 is the filter medium of embodiment 30 wherein the depthloading filter layer displays a DEHS filtration efficiency of up to99.97%.

Embodiment 32 is the filter medium of embodiment 31 wherein the depthloading filter layer displays a DEHS filtration efficiency of up to99.5%.

Embodiment 33 is the filter medium of any one of embodiments 1 through32 wherein the depth loading filter layer has a basis weight of up to150 g/m².

Embodiment 34 is the filter medium any one of embodiments 1 through 33wherein the depth loading filter layer has a basis weight of at least 10g/m².

Embodiment 35 is the filter medium of any one of embodiments 1 through34 wherein the depth loading filter layer displays a salt loadingcapacity of at least 1 g/m² at 500 Pascals pressure rise over initial.

Embodiment 36 is the filter medium of any one of embodiments 1 through35 wherein the depth loading filter layer displays a salt loadingcapacity of up to 10 g/m² at 500 Pascals pressure rise over initial.

Embodiment 37 is the filter medium of any one of embodiments 1 through36 wherein the support layer has a Gurley stiffness of 1000 milligramsor more.

Embodiment 38 is the filter medium of embodiment 27 wherein the supportlayer has an air permeability of at least 10 ft³/min at 125 Pa (80.2l/m²/sec at 200 Pa).

Embodiment 39 is the filter medium of any one of embodiments 1 through38 wherein the support layer comprises wet-laid fibers.

Embodiment 40 is the filter medium of embodiment 39 wherein the wet-laidfibers comprise cellulose, polyester, or combinations thereof.

Embodiment 41 is the filter medium of any one of embodiments 1 through40 wherein the support layer has a basis weight of up to 260 g/m².

Embodiment 42 is the filter medium of any one of embodiments 1 through41 wherein the support layer has a basis weight of at least 50 g/m².

Embodiment 43 is the filter medium of any one of embodiments 1 through42 further comprising a scrim layer disposed between the surface loadingfilter layer and the depth loading filter layer.

Embodiment 44 is the filter medium of any one of embodiments 1 through43 having a thickness of at least 10 mils (0.25 mm).

Embodiment 45 is the filter medium of any one of embodiments 1 through44 having a thickness of up to 60 mils (1.5 mm).

Embodiment 46 is the filter medium of embodiment 45 having a thicknessof up to 30 mils (0.76 mm).

Embodiment 47 is the filter medium of any one of embodiments 1 through46 wherein the layers are adhered together with adhesive, binder fibers,thermal bonding, ultrasonic bonding, self-adhesion, or combinationsthereof.

Embodiment 48 is the filter medium of any one of embodiments 1 through47 which displays an efficiency of at least F9 per EN779:2012.

Embodiment 49 is the filter medium of embodiment 48 which displays anefficiency of at least 80%, or greater than 80%, per the DEHS efficiencytest at the most penetrating particle size.

Embodiment 50 is the filter medium of any one of embodiments 1 through49 which is an air filter medium.

Embodiment 51 is a gas filter element comprising a housing and a gasfilter medium of any one of embodiments 1 through 50.

Embodiment 52 is the gas filter element of embodiment 51 which displaysan efficiency of at least F9 per EN779:2012.

Embodiment 53 is the gas filter element of embodiment 52 which displaysan efficiency of at least E10 per EN1822:2009.

Embodiment 54 is the gas filter element of embodiment 53 which displaysan efficiency of at least E11 per EN1822:2009.

Embodiment 55 is the gas filter element of embodiment 54 which displaysan efficiency of at least E12 per EN1822:2009.

Embodiment 56 is the gas filter element of any one of embodiments 51through 55 which is a flat panel, cylindrical, or conical.

Embodiment 57 is the gas filter element of any one of embodiments 51through 56 which is pleated.

Embodiment 58 is a method of filtering a gas (e.g., air), the methodcomprising directing the gas through a filter element of any one ofembodiments 51 through 57.

Embodiment 59 is a method of filtering a gas, the method comprisingdirecting the gas through a filter medium of any one of embodiments 1through 55.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this disclosure.

Test Methods

Salt Loading Test

A TSI 8130 bench is used to load a 100 cm² sample of filtration mediawith NaCl salt particles (0.33 μm mass median diameter) at aconcentration of 20 mg/m³. The flowrate in the bench was chosen torepresent real world conditions. The other settings for the bench are tobe run to the manufacturer's standards. The media is loaded anywherefrom 4 inches to 10 inches H₂O (1000-2500 Pa) of dP before the end ofthe test, depending on the requestors needs. Every minute the benchmeasures the amount of salt loaded, salt passed, and dP across themedia. This data is recorded by the bench. Before and after thecompletion of the test the sample is weighed, the difference in theweight is the salt loaded, and this value is used to calibrate thephotometer.

It has been found that media which has greater than 0.5 g/ft² (5.38g/m²) capacity when loaded to 2 inches H₂O pressure drop rise at mediavelocity of 10 feet per minute (fpm) (5.33 cm/sec) is a depth loadingmedia.

Modified ISO11057 Test Method for Filtration Characterization ofCleanable Filter Material

To determine the pulse clean-ability of a filter media, a modifiedversion of ISO11057 test method for filtration characterization ofcleanable filter media was used. The ISO standard has 5 phases. Phase 2of the test was used with modification as follows:

-   -   Primary leg flow rate: 2.54 m³/hr;    -   Secondary leg flow rate: 5.07 m³/hr;    -   Maximum Restriction 1800 Pa;    -   Dust feed rate: 2.0 g/m³;    -   Pulse strength: 0.1 MPa; and    -   200 seconds per cycle, 300 total cycles per test.

All other test conditions remain the same.

The pressure drop (dP) across the media immediately after pulse wasrecorded for each cycle. The final dP after 300 cycles and dP afterextrapolation to 3000 cycles were used to compare the performance ofpulse cleanable media. The extrapolation was done by curve fitting alogarithmic or power equation (whichever has the higher R²) to the data(to 300 pulses), then using the equation to determine the dP at 3000pulses.

DEHS Efficiency Test

A TSI 3160 bench is used to test the efficiency of a 100 cm² samplemedia at flows representative of real world conditions, in this case aflow of 4 feet per minute (fpm) was used. An atomizer creates adistribution of DEHS droplets and a Differential Mobility Analyzer (DMA)is used to classify a distribution of DEHS droplets into a cloud ofmonodisperse particles. The oil droplet sizes for this test are 0.09,0.1, 0.2, 0.3 and 0.4 μm. A Condensation Particle Counter (CPC) thenmeasures the challenge concentration upstream and downstream of thefilter sample in order to determine the media efficiency at thatparticle size. All other settings are to the manufacturersspecifications.

After the efficiency is determined for all particle sizes, the systemfits a curve to these points in order to determine what particle sizerelates to the highest penetration (lowest efficiency), this is calledthe most penetrating particle size (MPPS) and can be a calculatedpenetration based on the fitted curve for that particular media sample.

LEFS Test

A 4-inch diameter sample is cut from the media. Particle captureefficiency of the test specimen is calculated using 0.8 μm latex spheresas a test challenge contaminant in the LEFS (for a description of theLEFS test, see ASTM Standard F1215-89) bench operating at 20 fpm.

EXAMPLES Example 1

Laminated filter media were prepared using the following technique. A 50gsm wet-laid filter material that includes a mixture of glass andbicomponent PET fibers was prepared similar to that of Example 6 in U.S.Pat. No. 7,314,497 (with the modification that it consists of 40% B08micro glass fibers from Lauscha Fiber International (Lauscha, Germany)and 60% TJ04BN bicomponent PET fibers from Teijin (Osaka, Japan)). A 116gsm wet-laid media consisting of 90% cellulose and 10% polyester blendsupport material was purchased from H&V of East Walpole, MA The sheetproperties are in Table 1.

TABLE 1 Properties of the components of Example 1 Property Units EN937EN829 Basis Weight lbs./ 30.5 71.3 3000 ft² grams/m² 50 116 Fiber Sizeμm 0.8/14 N/A Thickness (1.5 pounds per inches 0.0071 0.012 square inch(psi)) mm 0.183 0.30 Air Permeability @ 0.5 inch (in) H₂O fpm 22.4 14.0(125 Pascals (Pa)) @ 200 Pascals (0.8 inch H₂O) l/m²/sec 179 111.9Hydrostatic Head mbar 8.00 50.0 Salt loaded at 2 inches H₂O g/ft² 0.4030.0374 dP rise at 10 fpm g/m² 4.33 0.403 Pre IPA MPPS DEHS % 95.14 <10%efficiency 4 fpm (2.0 centimeters/seconds (cm/sec)) Post IPA soak MPPSDEHS % 93.83 <10% efficiency 4 fpm (2.0 cm/sec)

These two rolls were layered so that the glass bicomponent layer wasupstream and the cellulose polyester blend was on the bottom. A granularadhesive from EMS-Griltech of Switzerland (Griltex 9E) was appliedbetween the two layers at a rate of 4.07 g/m², they were then heatlaminated at 265° F.

After lamination a fine fiber layer was applied to the 50 gsm glassbicomponent layer. This fine fiber layer was comprised of fibers sizedbetween 0.2 to 0.3 microns, and consisting of Nylon with a LEFSefficiency of 82.4%.

The laminated and nano-fiber coated media was tested for its flat sheetproperties and the element was tested for dP and efficiency using theEN1822 procedure. The results are shown in Table 2.

TABLE 2 Properties of the laminated media and element Example 1 Example1 (EX3326, (EX3326, before after Property and nano - fiber nano -fiberTest Results Units coating) coating) Basis Weight lbs./ 101.8 101.8 3000ft² gram/m² 166 166 Thickness (wedge foot) inches N/A 0.021 mm N/A 0.533Air Permeability @ 0.5 inch H₂O (125 Pa) fpm 6.1 5.9 @ 200 Pascals (0.8in. H₂O) l/m²/sec 48.9 47.3 Corrugation Depth inches N/A 0.018 mm N/A0.46 LEFS efficiency of the % — 82.4 fine fiber layer at 20 fpm (10.66cm/s) Pre IPA soak MPPS DEHS % 98.15 98.97 efficiency 4 fpm (2.0 cm/sec)Post IPA soak MPPS DEHS % 97.5 98.82 efficiency 4 fpm (2.0 cm/sec) Saltloaded at 2 inches H₂O g/m² N/A N/A dP rise at10 fpm ISO11057 (modified)dP Pa N/A 554 after 300 pulses ISO11057 (modified) dP Pa N/A 714 after3000 pulses (extrapolated) Element dP inches H₂O N/A 1.045 Pa 261Element efficiency at MPPS % N/A 99.541

The flat sheet media was pleated at 2 inches (5.1 cm) pleat depth andbuilt into a 26 inch (66 cm) conical and cylindrical filter pair. Theconical elements had 280 pleats per element while the cylindricalelements had 230 pleats. The elements were built such that thenano-fiber layer was facing upstream.

Example 2

Laminated filter media were prepared using the following technique. A 50gsm wet-laid filter material that includes a mixture of glass andbicomponent PET fibers was prepared similar to that of Example 6 in U.S.Pat. No. 7,314,497 (with the modification that it consists of 40% B08micro glass fibers from Lauscha Fiber International (Lauscha, Germany)and 60% TJ04BN bicomponent PET fibers from Teijin (Osaka, Japan)). A 116gsm wet-laid media consisting of 90% cellulose and 10% polyester blendsupport material was purchased from H&V of East Walpole, MA The sheetproperties are in Table 3.

TABLE 3 Properties of the components of Example 2 Property Units EN937EN829 Basis Weight lbs./ 30.5 71.3 3000 ft² grams/m² 50 116 Fiber Sizeμm 0.8/14 N/A Thickness (1.5 pounds per inches 0.0071 0.012 square inch(psi)) mm 0.183 0.30 Air Permeability @ 0.5 inch (in) H₂O fpm 22.4 14.0(125 Pascals (Pa)) @ 200 Pascals (0.8 inch H₂O) l/m²/sec 179 111.9Hydrostatic Head mb ar 8.00 50.0 Salt loaded at 2 inches H₂O g/ft² 0.400.037 dP rise at10 fpm g/m² 4.33 0.403 Pre IPA MPPS DEHS % 95.14 N/Aefficiency 4 fpm (2.0 cm/sec) Post IPA soak MPPS DEHS % 93.83 N/Aefficiency 4 fpm (2.0 cm/sec)

These two rolls were layered so that the glass bicomponent layer wasupstream and the cellulose polyester blend was on the bottom. The twolayers were heat laminated at 265° F. using Griltex 9E, a granularadhesive from (EMS-Griltech of Switzerland) at a rate of 4.07 g/m²between each layer. After lamination, a fine fiber layer was applied tothe 116 gsm wet-laid cellulose polyester blend layer. This fine fiberlayer was comprised of nylon fibers sized between 0.2 to 0.3 micron,with a LEFS efficiency of 78%. The laminated and nano-fiber coated mediawas tested for its flat sheet properties. The results are shown in Table4.

TABLE 4 Properties of the laminated media Example 2 Property Units(EX3092) Basis Weight lbs./3000 ft² 101.8 grams/m² 166.5 Thickness(wedge foot) inches 0.025 mm 0.635 Air Permeability @ 0.5 inch H₂O (125Pa) fpm 5.3 @ 200 Pascals (0.8 inch H₂O) l/m²/sec 42.9 Hydrostatic Headmb — ISO11057 (modified) dP after Pa 382 300 pulses ISO11057 (modified)dP after Pa 856 3000 pulses (extrapolated) Pre IPA MPPS DEHS % 99.46efficiency 4 fpm (2.0 cm/sec) Post IPA soak MPPS DEHS % 99.06 efficiency4 fpm (2.0 cm/sec)

The flat sheet media was pleated at 2 inches (5.1 cm) pleat depth andbuilt into a 26 inch (66 cm) conical and cylindrical filter pair. Theconical elements had 250 pleats per element while the cylindricalelements had 210 pleats. The elements were built such that thenano-fiber layer was facing upstream.

Example 3

Laminated filter media were prepared using the following technique. A 50gsm wet-laid filter material that includes a mixture of glass andbicomponent fibers was prepared similar to that of Example 6 in U.S.Pat. No. 7,314,497 (with the modification that it consists of 50% B08micro glass fibers from Lauscha Fiber International (Lauscha, Germany)and 50% bicomponent PET fibers (TJ04BN) from Teijin (Osaka, Japan)). A100 gsm spunbond support material of Finon C310NW was purchased fromMidwest Filtration of Cincinnati, OH. The sheet properties are in Table5.

TABLE 5 Properties of the components of Example 3 (EX3167) FINONProperty Units EN0701937 C310NW Basis Weight lbs./3000ft² 30.5 61.5grams/m² 50 100 Fiber Size μm 0.8/14 17.4 Thickness (1.5 psi) Inches0.0115 0.008 mm 0.292 0.203 Air Permeability @ 0.5 inch H₂O (125 Pa) fpm10.10 108.00 @ 200 Pascals (0.8 inch H₂O) l/m²/sec 81 864 HydrostaticHead mb 16.00 6.00 Salt loaded at 2 inches H₂O g/ft² 0.40 N/A dP rise at10 fpm g/m² 4.33 N/A Pre IPA MPPS DEHS % 98.81 <10% efficiency 4 fpm(2.0 cm/sec) Post IPA soak MPPS DEHS % 98.03 <10% efficiency 4 fpm (2.0cm/sec)

These two rolls were layered so that the wet-laid layer was in theupstream and the spunbond layer was downstream. The layers were heatlaminated at 275° F. using a granular adhesive Griltex 9E (EMS-Griltechof Switzerland) at a rate of 4.07 g/m² between each layer.

The material was then corrugated to an average depth of 0.027 inch (0.69mm) (measuring the distance in the z direction from the top of the peakto the bottom of the trough on the wire side of the media) with 4.5corrugations per inch (1.77 corrugations/cm). After corrugation, a finefiber layer was applied to the 50 gsm wet laid layer. This fine fiberlayer was comprised of nylon fibers sized between 0.2 to 0.3 micron,with a LEFS efficiency of 66%.

The laminated, corrugated, and coated media was tested for its flatsheet properties. The results are shown in Table 6.

TABLE 6 Properties of the laminated media Example 3 Example 3 beforeafter nano-fiber nano-fiber Property Units coating coating Basis Weightlbs./3000 ft² 92 92 grams/m² 150 150 Thickness (wedge foot) inches N/A0.0189 mm N/A 0.48 Air Permeability @ 0.5 inch H₂O (125 Pa) fpm 10.2810.20 @ 200 Pascals (0.8 inch H₂O) l/m²/sec 83.24 82.62 ISO11057(modified) dP after Pa N/A N/A 300 pulses ISO11057 (modified) dP afterPa N/A N/A 3000 pulses (extrapolated) Pre IPA MPPS DEHS % 98.38 99.55efficiency 4 fpm (2 cm/sec) Post IPA soak MPPS DEHS % 94.73 96.29efficiency 4 fpm (2 cm/sec) Corrugation Depth inches 0.027 0.0106 mm0.69 0.27

The flat sheet media was pleated at 2 inches (5.1 cm) pleat depth andbuilt into 26-inch (66 cm) conical and cylindrical filter pairs. Theconical elements had 210 pleats per element while the cylindricalelements had 176. The elements were built such that the nanofiber layerwas facing upstream.

Example 4

Laminated filter media were prepared using the following technique. A18.6 gsm spunbond scrim layer of FINON C3019 was purchased from MidwestFiltration of Cincinnati, OH A 50 gsm wet-laid filter material thatincludes a mixture of glass and bicomponent fibers was prepared similarto that of Example 6 in U.S. Pat. No. 7,314,497 (with the modificationthat it consists of 50% B08 micro glass fibers from Lauscha FiberInternational (Lauscha, Germany) and 50% bicomponent PET fibers (TJ04BN)from Teijin (Osaka, Japan)). A 100 gsm spunbond support material ofFinon C310NW was purchased from Midwest Filtration of Cincinnati, OH.The sheet properties are in Table 7.

TABLE 7 Properties of the components of Example 4 (EX3379) FINON FINONProperty Units C3019 EN937 C310NW Basis Weight lbs./ 11.4 30.5 61.5 3000ft² grams/m² 18.6 50 100 Fiber Size μm N/A 0.8/14 17.4 Thickness (1.5psi) inches 0.002 0.0115 0.008 mm 0.05 0.292 0.203 Air Permeability @0.5 inch H₂O (125 Pa) fpm 627 10.10 108 @ 200 Pascals (0.8 inch l/m²/sec5079 81.81 875 H₂O) Hydrostatic Head mb <6.00 16.00 6.00 Salt loaded at2 inches H₂O g/ft² N/A 0.40 N/A dP rise at 10 fpm g/m² N/A 4.33 N/A PreIPA MPPS DEHS % <10% 98.81 <10% efficiency 4 fpm (2 cm/sec) Post IPAsoak MPPS % <10% 98.03 <10% DEHS efficiency 4 fpm (2 cm/sec)

These three rolls were layered so that the scrim layer was upstream, thewet-laid layer was in the middle, and the spunbond layer was downstream.The layers were heat laminated at 275° F. using GRILTEX 9E granularadhesive (EMS-Griltech of Switzerland) at a rate of 4.07 g/m² betweeneach layer.

The material was then corrugated to an average depth of 0.0248 inch(0.63 mm) (measuring the distance in the z direction from the top of thepeak to the bottom of the trough on the wire side of the media) with 4.5corrugations per inch (1.77 corrugations/cm).

After corrugation, a fine fiber layer was applied to the 18.6 gsm spunbond scrim layer. This fine fiber layer was comprised of nylon fiberssized between 0.2 to 0.3 micron, with a LEFS efficiency of 66%. Thelaminated, corrugated and fine fiber coated media was tested for itsflat sheet properties. The results are shown in Table 8.

TABLE 8 Properties of the laminated media Example 4 Example 4 beforeafter nano-fiber nano-fiber Property Units coating coating Basis Weightlbs./ 103.4 103.4 3000 ft² grams/m² 168.6 168.6 Thickness (wedge foot)inches 0.018 0.019 mm 0.46 0.485 Air Permeability @ 0.5 inch H₂O (125Pa) fpm 8.91 8.18 @ 200 Pascals (0.8 inch H₂O) l/m²/sec 72.17 66.26 LEFSefficiency of the fine fiber % — 66 layer at 20 fpm (10.66 cm/s)ISO11057 (modified) dP after Pa N/A N/A 300 pulses ISO11057 (modified)dP after Pa N/A N/A 3000 pulses (extrapolated) Pre IPA MPPS DEHS % 99.4999.74 efficiency 4 fpm (2 cm/sec) Post IPA soak MPPS DEHS % 97.3 97.74efficiency 4 fpm (2 cm/sec) Corrugation Depth inches 0.024 0.0105 mm0.69 0.27

Example 5

Laminated filter media were prepared using the following technique. A 50gsm wet-laid filter material that includes a mixture of glass andbicomponent fibers was prepared similar to that of Example 6 in U.S.Pat. No. 7,314,497 (with the modification that it consists of 50% B04micro glass fibers from Lauscha Fiber International (Lauscha, Germany)and 50% bicomponent PET fibers (TJ04BN) from Teijin (Osaka, Japan)). A116 gsm corrugated cellulose support material was purchased from H&V ofEast Walpole, MA The sheet properties are in Table 9.

TABLE 9 Properties of the components of Example 5 (EX3396) PropertyUnits EN0701997 EN448 Basis Weight lbs./ 30.5 71.3 3000 ft² grams/m² 50116 Fiber Size μm 0.4/14 N/A Thickness (1.5 psi) inches 0.009 0.012 mm0.225 0.3 Air Permeability @ 0.5 inch H₂O (125 Pa) fpm 5.25 16 @ 200Pascals (0.8 inch H₂O) l/m²/sec 45.53 130 Hydrostatic Head mb N/A N/ASalt loaded at 2 inches H₂O g/ft² 0.3031 0.0777 dP rise at 10 fpm g/m²3.26 0.843 Pre IPA MPPS DEHS % 99.97 <10% efficiency 4 fpm (2 cm/sec)Post IPA soak MPPS DEHS % N/A <10% efficiency 4 fpm (2 cm/sec)

These two rolls were layered so that the wet-laid layer was upstream andthe cellulose wet-laid layer was downstream. The layers were heatlaminated at 275° F. using Griltex 9E granular adhesive (EMS-Griltech ofSwitzerland) at a rate of 4.07 g/m² between each layer.

After lamination, a fine fiber layer was applied to the 50 gsm wet-laidlayer. This fine fiber layer was comprised of nylon fibers sized between0.2 to 0.3 micron, with a LEFS efficiency of 74%.

The laminated and fine fiber coated media was tested for its flat sheetproperties. The results are shown in Table 10.

TABLE 10 Properties of the laminated media Example 5 Example 5 beforeafter nano-fiber nano-fiber Property Units coating coating Basis Weightlbs./ 101.8 101.8 3000 ft² grams/m² 161.3 161.3 Thickness (wedge foot)inches 0.021 0.020 mm 0.53 0.51 Air Permeability @ 0.5 inch H₂O (125 Pa)fpm 3.5 3.23 @ 200 Pascals (0.8 inch H₂O) l/m²/sec 28.4 26.16 ISO11057(modified) dP after Pa N/A N/A 300 pulses ISO11057 (modified) dP afterPa N/A N/A 3000 pulses (extrapolated) Pre IPA MPPS DEHS % 99.98 98.75efficiency 4 fpm (2 cm/sec) Post IPA soak MPPS DEHS % 99.85 97.48efficiency 4 fpm (2 cm/sec) Corrugation Depth inches 0.0207 0.0195 mm0.53 0.48

The flat sheet media was pleated at 2 inches (5.1 cm) pleat depth andbuilt into a 26 inch (66 cm) cylindrical filter pair. The elements had250 pleats per element. The elements were built such that the nano-fiberlayer was facing upstream.

Example 6

Laminated filter media were prepared using the following technique. A 50gsm wet-laid filter material that includes a mixture of glass andbicomponent PET fibers was prepared similar to that of Example 6 in U.S.Pat. No. 7,314,497 (with the modification that it consists of 40% B08micro glass fibers from Lauscha Fiber International (Lauscha, Germany)and 60% TJ04BN bicomponent PET fibers from Teijin (Osaka, Japan)). A 114gsm wet-laid media consisting of glass, polyester, and resin supportmaterial was purchased from H&V of East Walpole, MA The sheet propertiesare in Table 11.

TABLE 11 Properties of the components of Example 6 (EX3380) PropertyUnits EN937 EN933 Basis Weight lbs./ 30 70 3000 ft² grams/m² 50 114Fiber Size μm 0.8/14 N/A Thickness (1.5 psi) inches 0.0071 0.022 mm0.183 0.56 Air Permeability @ 0.5 inch H₂O (125 Pascals) fpm 22.4 54 @200 Pascals (0.8 inch H₂O) l/m²/sec 181.4 437 Hydrostatic Head mbar 8.00N/A Salt loaded at 2 inches H₂O g/ft² 0.40 0.23 dP rise at 10 fpm g/m²4.33 2.49 Pre IPA MPPS DEHS % 95.14 <10% efficiency 4 fpm (2.0 cm/sec)Post IPA soak MPPS DEHS % 93.83 <10% efficiency 4 fpm (2.0 cm/sec)

The EN933 material was corrugated to an average depth of 0.0283 inch(0.72 mm) (measuring the distance in the z direction from the top of thepeak to the bottom of the trough on the wire side of the media) with 4.5corrugations per inch (1.77 corrugations/cm).

These two rolls were then layered so that the glass bicomponent layerwas upstream and the glass polyester blend was on the bottom. The twolayers were heat laminated at 265° F. using Griltex 9E, a granularadhesive from (EMS-Griltech of Switzerland) at a rate of 4.07 g/m²between each layer.

After lamination a fine fiber layer was applied to the 50 gsm wet laidlayer. This fine fiber layer was comprised of nylon fibers sized between0.2 to 0.3 micron, with a LEFS efficiency of 62.4%. The laminated andnano-fiber coated media was tested for its flat sheet properties, theresults are shown in Table 12.

TABLE 12 Properties of the laminated media Example 6 Example 6 beforeafter Property and nano-fiber nano-fiber test results Units coatingcoating Basis Weight lbs./ 100 100 3000 ft² gram/m² 164 164 Thickness(wedge foot) inches 0.023 0.021 mm 0.584 0.533 Air Permeability @ 0.5inch H₂O (125 Pa) fpm 8.6 8.6 @ 200 Pascals (0.8 inch H₂O) l/m²/sec 69.769.7 Corrugation Depth inches 0.0195 0.022 mm 0.496 0.56 ISO11057(modified) dP after Pa N/A 448 300 pulses ISO11057 (modified) dP afterPa N/A 696 3000 pulses (extrapolated) Pre IPA MPPS DEHS % 99.34 99.43efficiency 4 fpm (2.0 cm/sec) Post IPA soak MPPS DEHS % 98.62 98.66efficiency 4 fpm (2.0 cm/sec)

The flat sheet media was pleated at 2 inches (5.1 cm) pleat depth andbuilt into a 26 inch (66 cm) conical and cylindrical filter pair. Theconical elements had 266 pleats per element while the cylindricalelements had 220 pleats. The elements were built such that thenano-fiber layer was facing upstream.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this disclosure will become apparent tothose skilled in the art without departing from the scope and spirit ofthis disclosure. It should be understood that this disclosure is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the disclosureintended to be limited only by the claims set forth herein as follows.

What is claimed:
 1. A gas filter medium comprising: a surface loadingfilter layer; a depth loading filter layer comprising glass fibers andmulti-component binder fibers, wherein the depth loading filter layerdisplays a salt loading capacity of at least 1 g/m² at 500 Pascalspressure rise over initial; and a support layer having a Gurleystiffness of 1000 milligrams or more; wherein the layers are configuredand arranged for placement in a gas stream with the surface loadingfilter layer being the most upstream layer.
 2. The filter medium ofclaim 1 further comprising one or more additional layers comprising asurface loading filter layer, a depth loading filter layer, or a supportlayer.
 3. The filter medium of claim 1 which is pulse cleanableaccording to Modified ISO 11057 Test Method.
 4. The filter medium ofclaim 1 wherein the depth loading filter layer is positioned between thesurface loading layer and the support layer.
 5. The filter medium ofclaim 1 wherein the surface loading filter layer comprises fine fiberscomprising nylon, polyvinylidene fluoride, polyurethane, or combinationsthereof.
 6. The filter medium of claim 1 wherein the surface loadingfilter layer has a LEFS filtration efficiency of at least 30%.
 7. Thefilter medium of claim 1 wherein the depth loading filter layercomprises a high-efficiency melt-blown filter layer.
 8. The filtermedium of claim 1 wherein the depth loading filter layer displays a DEHSfiltration efficiency of at least 55%.
 9. The filter medium of claim 1wherein the depth loading filter layer has a basis weight of up to 150g/m².
 10. The filter medium of claim 1 wherein the support layer has anair permeability of at least 10 ft³/min at 125 Pa.
 11. The filter mediumof claim 1 wherein the support layer has an air permeability of at least80.2 l/m²/sec at 200 Pa.
 12. The filter medium of claim 1 wherein thedepth loading filter layer comprises a hydrophobic coating.
 13. Thefilter medium of claim 1 wherein the support layer has a basis weight ofup to 260 g/m².
 14. The filter medium of claim 1 having a thickness ofat least 10 mils (0.25 mm).
 15. The filter medium of claim 1 whichdisplays an efficiency of at least F9 per EN779:2012.
 16. The filtermedium of claim 15 which displays a filtration efficiency of at least80%, per the DEHS efficiency test at the most penetrating particle size.17. The filter medium of claim 1 wherein the support layer compriseswet-laid fibers comprising cellulose, polyester, or combinationsthereof.
 18. The filter medium of claim 1 wherein the layers are adheredtogether with adhesive, binder fibers, thermal bonding, ultrasonicbonding, self-adhesion, or combinations thereof.
 19. The filter mediumof claim 1 which is an air filter medium.
 20. The filter medium of claim1 wherein the surface loading filter layer comprises an oleophobiccoating.
 21. A gas filter element comprising a housing and a gas filtermedium of claim
 1. 22. A gas filter medium comprising: a surface loadingfilter layer; a depth loading filter layer comprising a high-efficiencyfilter layer comprising glass fibers and multi-component binder fibers;wherein the depth loading filter layer displays a DEHS filtrationefficiency of at least 55% and a salt loading capacity of at least 1g/m² at 500 Pascals pressure rise over initial; and a support layer;wherein the layers are configured and arranged for placement in a gasstream with the surface loading filter layer being the most upstreamlayer, and wherein the gas filter medium has a thickness of 0.25 mm to0.76 mm.
 23. A gas filter medium comprising: a surface loading filterlayer; a depth loading filter layer comprising a high-efficiency filterlayer comprising glass fibers and multi-component binder fibers; whereinthe depth loading filter layer displays a DEHS filtration efficiency ofat least 55% and a salt loading capacity of at least 1 g/m² at 500Pascal pressure rise over initial; a support layer having a Gurleystiffness of 1000 milligrams or more; wherein the layers are configuredand arranged for placement in a gas stream with the surface loadingfilter layer being the most upstream layer.